1. Field of the Invention
This invention relates to the general field of manufacturing and more particularly to the positioning of tools for carrying out manufacturing or inspection operations.
2. Discussion of Prior Arts
In a manufacturing environment, it is generally necessary to perform operations such as measuring, drilling, cutting, countersinking, and inspecting, for example. Tools for carrying out these operations need to be positioned prior to performing their function.
The accuracy with which the tools are positioned is dependent upon the level of accuracy required in the finished product. For example, in aircraft manufacture, many components need to be produced to very high standards of accuracy, and are often fitted and finished by hand to meet the required tolerances.
Traditionally, articles being manufactured would be marked up by hand, to show where holes should be drilled or the material should be cut for example. This method is time consuming and costly, as it relies heavily on skilled labor. More recently, articles have been held in jigs or other fixtures designed to hold a particular article in a desired position whilst it is machined or inspected using, for example, a numerically controlled machine.
For smaller batches of articles, it is often prohibitively expensive to obtain the tooling, such as jigs or other fixtures, which permits highly accurate manufacture of the articles.
The present invention seeks to alleviate the problem. of expense associated with the known tool positioning methods described above, by providing an apparatus and a method for accurately positioning tools for use in manufacturing or inspection operations whilst reducing the need for costly tooling such as jigs.
According to the present invention there is provided:
A micropositioning system comprising:
a radiation source for projecting an image onto a surface of an article, the image being part of a manufacturing template and the image representing a predetermined position on the surface of the article where a manufacturing or inspection operation is to be undertaken;
a radiation detector for detecting the projected image;
tool conveyancing means for carrying a tool adapted to perform manufacturing or inspection operations;
processor means for calculating at least two dimensional co-ordinates of the projected image detected by the radiation detector relative to the tool; and
control means for controlling the tool conveyancing means so as to position the tool in a predefined spacial relationship with the projected image in response to a signal from the processor means.
Advantageously the information contained within the manufacturing template is obtained directly from a CAD model of the article.
The radiation source may be a laser. Advantageously the radiation source provides radiation visible to the human eye so that an operator may view the image. The radiation source may be for example a Virtek Laseredge 3D laser projection system. Two radiation sources may be used for complex surfaces.
The radiation source may project an image in the form of an ellipse. The radiation source may alternatively project an image in the form of a cross, or a circle. The image is preferably of a size in the range 0.5 to 3.0 cm.
The image is projected onto a surface at a location where a manufacturing or inspection operation is to be carried out. Several images may be simultaneously projected to provide, for example, a drill template on a surface such as an aircraft panel.
The radiation detector preferably comprises a camera and an image processing system. The camera may comprise an array of solid state charge coupled devices (CCDs). The array may be linear or rectangular. The CCDs produce a charge proportional to the amount of light falling on them and the charge from each device in the array is preferably used by the image processing system to build up an image.
The image processing system preferably comprises a frame grabber for digitising the image and a computer adapted for processing the image.
The image is advantageously processed by the computer to identify features such as areas of the same intensity or changes in intensity, for example. The image processor advantageously is thereby able to identify an image such as a cross projected by the radiation source, and locate the centre of the image.
The tool conveyancing means may comprise a tool holding device, for example, a chuck. The tool conveyancing means preferably further comprises a moveable stage. The tool holding device is advantageously mounted on the moveable stage. The moveable stage is preferably able to move in at least x and y directions, where the x and y directions are normal to each other and are in one plane (the x-y plane). The moveable stage may be servo motor actuated. The moveable stage may additionally be able to move in a z direction, where the z direction is normal to the x-y plane. Alternatively the tool holding device may be adapted to move in the z direction. The tool holding device is advantageously mounted to the moveable stage in a manner such that the tool holding device may move relative to the moveable stage in the z direction.
The moveable stage is preferably mounted on a platform, such that it is able to move relative to the platform. The platform preferably comprises attachment means for allowing the platform to be releasably attached to the surface. The attachment means may comprise a vacuum sucker. The vacuum sucker may comprise a rubber seal and venturi ejector vacuum pump. Alternatively the attachment means may comprise a magnetic portion, if the surface is ferrous. Alternatively the attachment means may comprise a mechanical fastener, such as a bolt or clamp, for example.
The platform may comprise one or more adjustable feet for allowing the micropositioning system to operate on curved or uneven surfaces. The adjustable feet are preferably individually adjustable, and are for adjusting the distance between the surface and the platform. The adjustable feet may be manually or automatically adjustable, and may utilise hydraulic or electrical jacks, or telescopic or screw thread mechanical arrangements.
The micropositioning system preferably comprises normalisation means for checking that the tool is substantially normal to the surface prior to a manufacturing operation being carried out. The normalisation means may automatically control the adjustable feet to ensure that the platform is stable with respect to the surface and to alter the orientation of the platform and with it the inclination of the tool.
The normalisation means may comprise a sensor such as, for example, a linear potentiometer. The normalisation means may comprise at least two sensors located on the platform in a manner such that, in use, the sensors are adjacent the surface. Alternatively the normalisation means may comprise a sensor such as, for example, a radiation source and reflected radiation detector system, where at least two such sensors are located on the platform such that, in use, the sensors are perpendicular to the surface. The sensors are preferably used to determine if the moveable stage of the platform is substantially parallel to the surface in cases where the surface is substantially flat, or in the case of a curved surface, whether the moveable stage mounted on the platform is substantially tangential to the surface. The normalisation means may further comprise a tool normalisation aid for checking that the tool is normal to the moveable stage.
The processor means advantageously uses data obtained from the image processing system to determine the location of the image with respect to the position of the tool.
The control means may comprise a servo motor and a motion controller.
The control means preferably comprises at least two servo motors, at least one for actuating movement of the moveable stage in the x direction and at least one for actuating movement of the moveable stage in the y direction.
The motion controller advantageously controls the movement of the moveable stage in at least the x and y directions.
The control means may further comprise a servo motor for actuating movement of the tool holder in the z direction. The motion controller may control the movement of the tool holder in the z direction.
The processor means are adapted to communicate with the control means.
The tool conveyancing means may comprise an extendable arm for holding a tool. The tool may be a drill. Alternatively the tool may be a milling tool or a grinding tool or a welding tool or a rivet insertion tool. Alternatively the tool may be an inspection tool or a non destructive testing tool. Alternatively the tool may be a spray gun or blast gun.
A camera may be provided on the tool holder, for sending a xe2x80x98tool""s eye viewxe2x80x99 to a monitor visible to the micropositioning device operator. The operator is then able to visually verify that the operation is being carded out on the surface correctly and at the place where the image is being projected.
The platform, moveable plate and tool holding means are preferably mainly manufactured from a material having light weight and good strength, for example, aluminum alloy or carbon fibre composite.
A handle is preferably provided on the platform for enabling an operator to position the platform on the surface to drilled.
According to the present invention in another aspect thereof, there is provided a method for accurately positioning tools comprising at least the steps of:
projecting an image onto a surface of an article, the image being part of a manufacturing template and the image representing a predetermined position on the surface of the article where a manufacturing or inspection operation is to be undertaken;
detecting the projected image;
processing the projected image;
calculating at least two dimensional co-ordinates of the projected image relative to a tool adapted to perform manufacturing or inspection operations; and
moving the tool so that it is positioned in a predefined spacial relationship with respect to the projected image.
During processing of the image, preferably a feature such as an area having a greater intensity than its surroundings is identified by an image processing system. The centre of the area may then be determined by the image processing system. Alternatively a feature such as a change in intensity between adjacent areas may be identified by the image processing system, corresponding to a boundary of a projected image.
Preferably the image processing system locates the centre of the projected image. The two dimensional co-ordinates of the centre of the projected image relative to a tool are then advantageously calculated by a processor.
To assist the image processing system, the lighting is preferably controlled to give a high contrast between the projected image on the surface and the rest of the surface. Advantageously, the lighting is chosen to minimise unwanted reflections, shadows, and other uneven illumination.
Advantageously the tool is manoeuvrable in the x, y and z directions, where the x and y directions preferably represent a two dimensional plane substantially parallel or tangential to the surface and the z direction is normal to the x, y plane.
The tool is preferably held in an x, y plane substantially parallel or tangential to the surface, and displaced in the z direction toward or away from the surface. Advantageously prior to use the tool is normalised so that in use its line of action is normal to the surface.
Following calculation of the two dimensional co-ordinates of the centre of the projected image relative to the tool, the processor sends a signal to cause the tool to be moved in the x, y plane so that it is located at the same x, y co-ordinates as the centre of the projected image. The motion of the tool in the x, y plane is preferably achieved by a servo motor. Advantageously one servo motor controls movement in the x direction and one motor controls movement in the y direction. The servo motors are preferably controlled by a motion controller which receives move command instructions from the processor. The processor works out how the tool needs to move in the x and y directions to be at the same x and y coordinates as the centre of the image and then instructs the motion controller to actuate the servo motors to achieve this movement.
Feedback from the servo motors allows an operator to confirm that the tool has moved to the required x, y position.
When the tool is in the required x, y position the tool is then automatically displaced in the z direction, and enabled to carry out its operation.
The movement of the tool in the z direction may be achieved for example by a pneumatic cylinder or by a servo motor. The rate of movement in the z direction of the tool is preferably controlled by an adjustable spring damper unit.
Advantageously the platform is releasably attached to the surface by the operator prior to undertaking a manufacturing operation.
After projecting an image onto the surface, the operator may position the platform adjacent the projected image. The operator then preferably checks that the platform is positioned correctly. This check may be undertaken using normalisation sensors. Preferably the tool is prevented from operating when the normalisation sensors indicate that the platform is not positioned correctly. The normalisation sensors may control the movement of adjustable feet to ensure that the platform is stable with respect to the surface, and to alter the orientation of the platform. Alternatively the operator may manually control the movement of the adjustable feet.
Prior to a manufacturing operation being undertaken, the micropositioning system is preferably calibrated to allow the x, y co-ordinates within the field of view of the radiation detector to be linked to the x, y position of the tool. This allows the processor, once the x, y co-ordinates of an image within the field of view of the radiation detector has been determined, to work out the distance the tool needs to move in the x and y directions in order to be positioned at the same x, y coordinates as the image.
Preferably, following a manufacturing operation, the operator is able to visually inspect the result of the operation on a monitor, the monitor receiving an image of the surface from a camera located adjacent the tool.